Internet Engineering Task Force (IETF) F. Zhang, Ed.
Request for Comments: 7139 Huawei
Updates: 4328 G. Zhang
Category: Standards Track CATR
ISSN: 2070-1721 S. Belotti
Alcatel-Lucent
D. Ceccarelli
Ericsson
K. Pithewan
Infinera
March 2014
GMPLS Signaling Extensionsfor Control of Evolving G.709 Optical Transport Networks
Abstract
ITU-T Recommendation G.709 [G709-2012] introduced new Optical channel
Data Unit (ODU) containers (ODU0, ODU4, ODU2e, and ODUflex) and
enhanced Optical Transport Network (OTN) flexibility.
This document updates the ODU-related portions of RFC 4328 to provide
extensions to GMPLS signaling to control the full set of OTN
features, including ODU0, ODU4, ODU2e, and ODUflex.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7139.
Zhang, et al. Standards Track [Page 1]

RFC 7139 GMPLS Extensions for G.709 March 20141. Introduction
With the evolution and deployment of Optical Transport Network (OTN)
technology, it is necessary that appropriate enhanced control
technology support be provided for [G709-2012].
[RFC7062] provides a framework to allow the development of protocol
extensions to support GMPLS and Path Computation Element (PCE)
control of OTN as specified in [G709-2012]. Based on this framework,
[RFC7096] evaluates the information needed by the routing and
signaling process in OTNs to support GMPLS control of OTN.
[RFC4328] describes the control technology details that are specific
to the 2001 revision of the G.709 specification. This document
updates the ODU-related portions of [RFC4328] to provide Resource
Reservation Protocol - Traffic Engineering (RSVP-TE) extensions to
support control for [G709-2012].
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. GMPLS Extensions for the Evolving G.709 -- Overview
New features for the evolving OTN, for example, new ODU0, ODU2e,
ODU4, and ODUflex containers, are specified in [G709-2012]. The
corresponding new Signal Types are summarized below:
- Optical channel Transport Unit (OTUk):
o OTU4
- Optical channel Data Unit (ODUk):
o ODU0
o ODU2e
o ODU4
o ODUflex
A new tributary slot granularity (i.e., 1.25 Gbps) is also described
in [G709-2012]. Thus, there are now two tributary slot (TS)
granularities for the foundation OTN ODU1, ODU2, and ODU3 containers.
The TS granularity at 2.5 Gbps is used on the legacy interfaces while
the new 1.25 Gbps is used on the new interfaces.
Zhang, et al. Standards Track [Page 3]

RFC 7139 GMPLS Extensions for G.709 March 2014
In addition to the support of ODUk mapping into OTUk (k = 1, 2, 3,
4), [G709-2012] encompasses the multiplexing of ODUj (j = 0, 1, 2,
2e, 3, flex) into an ODUk (k > j), as described in Section 3.1.2 of
[RFC7062].
Virtual Concatenation (VCAT) of Optical channel Payload Unit-k (OPUk)
(OPUk-Xv, k = 1/2/3, X = 1...256) is also supported by [G709-2012].
Note that VCAT of OPU0 / OPU2e / OPU4 / OPUflex is not supported per
[G709-2012].
[RFC4328] describes GMPLS signaling extensions to support the control
for the 2001 revision of the G.709 specification. However, [RFC7096]
does not provide the means to signal all the new Signal Types and
related mapping and multiplexing functionalities. Moreover, it
supports only the deprecated auto-MSI (Multiframe Structure
Identifier) mode, which assumes that the Tributary Port Number (TPN)
is automatically assigned in the transmit direction and not checked
in the receive direction.
This document extends the G.709 Traffic Parameters described in
[RFC4328] and presents a new flexible and scalable OTN-TDM
Generalized Label format. (Here, TDM refers to Time-Division
Multiplexing.) Additionally, procedures about Tributary Port Number
assignment through the control plane are also provided in this
document.
4. Generalized Label Request
The GENERALIZED_LABEL_REQUEST object, as described in [RFC3471],
carries the Label Switched Path (LSP) Encoding Type, the Switching
Type, and the Generalized Protocol Identifier (G-PID).
[RFC4328] extends the GENERALIZED_LABEL_REQUEST object, introducing
two new code-points for the LSP Encoding Type (i.e., G.709 ODUk
(Digital Path) and G.709 Optical Channel) and adding a list of G-PID
values in order to accommodate the 2001 revision of the G.709
specification.
This document follows these extensions and introduces a new Switching
Type to indicate the ODUk Switching Capability [G709-2012] in order
to support backward compatibility with [RFC4328], as described in
[RFC7062]. The new Switching Type (OTN-TDM Switching Type) is
defined in [RFC7138].
Zhang, et al. Standards Track [Page 4]

RFC 7139 GMPLS Extensions for G.709 March 2014
Multiplier (MT): 16 bits
As defined in Section 3.2.4 of [RFC4328]. This field MUST be set
to 1 for ODUflex Signal Types.
Bit_Rate: 32 bits
In the case of ODUflex, including ODUflex(CBR) and ODUflex(GFP)
Signal Types, this field indicates the nominal bit rate of ODUflex
expressed in bytes per second, encoded as a 32-bit IEEE single-
precision floating-point number (referring to [RFC4506] and
[IEEE]). For other Signal Types, this field MUST be set to zero
on transmission, MUST be ignored on receipt, and SHOULD be passed
unmodified by transit nodes.
5.1. Usage of ODUflex(CBR) Traffic Parameters
In the case of ODUflex(CBR), the Bit_Rate information carried in the
ODUflex Traffic Parameters MUST be used to determine the actual
bandwidth of ODUflex(CBR) (i.e., Bit_Rate * (1 +/- Tolerance)).
Therefore, the total number of tributary slots N in the HO ODUk link
can be reserved correctly. Where:
N = Ceiling of
ODUflex(CBR) nominal bit rate * (1 + ODUflex(CBR) bit rate tolerance)
---------------------------------------------------------------------
ODTUk.ts nominal bit rate * (1 - HO OPUk bit rate tolerance)
In this formula, the ODUflex(CBR) nominal bit rate is the bit rate of
the ODUflex(CBR) on the line side, i.e., the client signal bit rate
after applying the 239/238 factor (according to Clause 7.3, Table 7-2
of [G709-2012]) and the transcoding factor T (if needed) on the CBR
client. According to Clauses 17.7.3, 17.7.4, and 17.7.5 of
[G709-2012]:
ODUflex(CBR) nominal bit rate = CBR client bit rate * (239/238) / T
The ODTUk.ts (Optical channel Data Tributary Unit k with ts tributary
slots) nominal bit rate is the nominal bit rate of the tributary slot
of ODUk, as shown in Table 1 (referring to Table 7-7 of [G709-2012]).
Zhang, et al. Standards Track [Page 8]

RFC 7139 GMPLS Extensions for G.709 March 2014
In this way, the number of required tributary slots for the
ODUflex(GFP) (i.e., the value of "n" in Table 2) can be deduced from
the Bit_Rate field.
5.3. Notification on Errors of OTN-TDM Traffic Parameters
There is no Adspec associated with the OTN-TDM SENDER_TSPEC object.
Either the Adspec is omitted or an Int-serv Adspec with the Default
General Characterization Parameters and Guaranteed Service fragment
is used (see [RFC2210]).
For a particular sender in a session, the contents of the OTN-TDM
FLOWSPEC object received in a Resv message SHOULD be identical to the
contents of the OTN-TDM SENDER_TSPEC object received in the
corresponding Path message. If the objects do not match, a ResvErr
message with a "Traffic Control Error/Bad Flowspec value" error MUST
be generated.
Intermediate and egress nodes MUST verify that the node itself, and
the interfaces on which the LSP will be established, can support the
requested Signal Type, NVC, and Bit_Rate values. If the requested
value(s) cannot be supported, the receiver node MUST generate a
PathErr message with a "Traffic Control Error/Service unsupported"
indication (see [RFC2205]).
In addition, if the MT field is received with a zero value, the node
MUST generate a PathErr message with a "Traffic Control Error/Bad
Tspec value" indication (see [RFC2205]).
Further, if the Signal Type is not ODU1, ODU2, or ODU3, and the NVC
field is not 0, the node MUST generate a PathErr message with a
"Traffic Control Error/Bad Tspec value" indication (see [RFC2205]).
Zhang, et al. Standards Track [Page 11]

RFC 7139 GMPLS Extensions for G.709 March 20146. Generalized Label
This section defines the format of the OTN-TDM Generalized Label.
6.1. OTN-TDM Switching Type Generalized Label
The following is the GENERALIZED_LABEL object format that MUST be
used with the OTN-TDM Switching Type:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TPN | Reserved | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Bit Map ...... ~
~ ...... | Padding Bits ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The OTN-TDM GENERALIZED_LABEL object is used to indicate how the LO
ODUj signal is multiplexed into the HO ODUk link. Note that the LO
OUDj Signal Type is indicated by Traffic Parameters, while the type
of HO ODUk link is identified by the selected interface carried in
the IF_ID RSVP_HOP object.
TPN: 12 bits
Indicates the TPN for the assigned tributary slot(s).
- In the case of an LO ODUj multiplexed into an HO
ODU1/ODU2/ODU3, only the lower 6 bits of the TPN field are
significant; the other bits of the TPN field MUST be set to 0.
- In the case of an LO ODUj multiplexed into an HO ODU4, only the
lower 7 bits of the TPN field are significant; the other bits
of the TPN field MUST be set to 0.
- In the case of ODUj mapped into OTUk (j=k), the TPN is not
needed, and this field MUST be set to 0.
Per [G709-2012], the TPN is used to allow for correct
demultiplexing in the data plane. When an LO ODUj is multiplexed
into an HO ODUk occupying one or more TSs, a new TPN value is
configured at the two ends of the HO ODUk link and is put into the
related MSI byte(s) in the OPUk overhead at the (traffic) ingress
end of the link, so that the other end of the link can learn which
TS(s) is/are used by the LO ODUj in the data plane.
Zhang, et al. Standards Track [Page 12]

RFC 7139 GMPLS Extensions for G.709 March 2014
the value of the Length field. In the context of [G709-2012], the
values of 4 and 16 indicate a TS granularity of 2.5 Gbps, and the
values 2, 8, 32, and 80 indicate a TS granularity of 1.25 Gbps.
In the case of an ODUk mapped into OTUk, there is no need to
indicate which tributary slots will be used, so the Length field
MUST be set to 0.
Bit Map: variable
Indicates which tributary slots in the HO ODUk that the LO ODUj
will be multiplexed into. The sequence of the Bit Map is
consistent with the sequence of the tributary slots in the HO
ODUk. Each bit in the bit map represents the corresponding
tributary slot in the HO ODUk with a value of 1 or 0 indicating
whether the tributary slot will be used by the LO ODUj or not.
Padding Bits
Are added after the Bit Map to make the whole label a multiple of
four bytes if necessary. Padding bits MUST be set to 0 and MUST
be ignored on receipt.
6.2. Procedures
The ingress node MUST generate a Path message and specify the OTN-TDM
Switching Type and corresponding G-PID in the
GENERALIZED_LABEL_REQUEST object, which MUST be processed as defined
in [RFC3473].
The ingress node of an LSP MAY include a Label ERO (Explicit Route
Object) subobject to indicate the label in each hop along the path.
Note that the TPN in the Label ERO subobject need not be assigned by
the ingress node. When the TPN is assigned by a node, the node MUST
assign a valid TPN value and then put this value into the TPN field
of the GENERALIZED_LABEL object when receiving a Path message.
In order to create bidirectional LSP, the ingress node and upstream
node MUST generate an UPSTREAM_LABEL object on the outgoing interface
to indicate the reserved TSs of ODUk and the assigned TPN value in
the upstream direction. This UPSTREAM_LABEL object is sent to the
downstream node via a Path massage for upstream resource reservation.
The ingress node or upstream node MAY generate a LABEL_SET object to
indicate which labels on the outgoing interface in the downstream
direction are acceptable. The downstream node will restrict its
choice of labels, i.e., TS resource and TPN value, to one that is in
the LABEL_SET object.
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RFC 7139 GMPLS Extensions for G.709 March 2014
The ingress node or upstream node MAY also generate a SUGGESTED_LABEL
object to indicate the preference of TS resource and TPN value on the
outgoing interface in the downstream direction. The downstream node
is not required to use the suggested labels; it may use another label
based on local decision and send it to the upstream node, as
described in [RFC3473].
When an upstream node receives a Resv message containing a
GENERALIZED_LABEL object with an OTN-TDM label, it MUST first
identify which ODU Signal Type is multiplexed or mapped into which
ODU Signal Type according to the Traffic Parameters and the IF_ID
RSVP_HOP object in the received message.
- In the case of ODUj-to-ODUk multiplexing, the node MUST retrieve
the reserved tributary slots in the ODUk by its downstream
neighbor node according to the position of the bits that are set
to 1 in the Bit Map field. The node determines the TS granularity
(according to the total TS number of the ODUk or pre-configured TS
granularity), so that the node can multiplex the ODUj into the
ODUk based on the TS granularity. The node MUST also retrieve the
TPN value assigned by its downstream neighbor node from the label
and fill the TPN into the related MSI byte(s) in the OPUk overhead
in the data plane, so that the downstream neighbor node can check
whether the TPN received from the data plane is consistent with
the Expected MSI (ExMSI) and determine whether there is any
mismatch defect.
- In the case of ODUk-to-OTUk mapping, the size of the Bit Map field
MUST be 0, and no additional procedure is needed.
When a downstream node or egress node receives a Path message
containing a GENERALIZED_LABEL_REQUEST object for setting up an ODUj
LSP from its upstream neighbor node, the node MUST generate an OTN-
TDM label according to the Signal Type of the requested LSP and the
available resources (i.e., available tributary slots of ODUk) that
will be reserved for the LSP and send the label to its upstream
neighbor node.
- In the case of ODUj-to-ODUk multiplexing, the node MUST first
determine the size of the Bit Map field according to the Signal
Type and the tributary slot type of ODUk and then set the bits to
1 in the Bit Map field corresponding to the reserved tributary
slots. The node MUST also assign a valid TPN, which MUST NOT
collide with other TPN values used by existing LO ODU connections
in the selected HO ODU link, and configure the Expected MSI
(ExMSI) using this TPN. Then, the assigned TPN MUST be filled
into the label.
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RFC 7139 GMPLS Extensions for G.709 March 2014
- In the case of ODUk-to-OTUk mapping, the TPN field MUST be set to
0. Bit Map information is not required and MUST NOT be included,
so the Length field MUST be set to 0 as well.
6.2.1. Notification on Label Error
When an upstream node receives a Resv message containing a
GENERALIZED_LABEL object with an OTN-TDM label, the node MUST verify
if the label is acceptable. If the label is not acceptable, the node
MUST generate a ResvErr message with a "Routing problem/Unacceptable
label value" indication. Per [RFC3473], the generated ResvErr
message MAY include an ACCEPTABLE_LABEL_SET object. With the
exception of label semantics, a downstream node processing a received
ResvErr message and ACCEPTABLE_LABEL_SET object is not modified by
this document.
Similarly, when a downstream node receives a Path message containing
an UPSTREAM_LABEL object with an OTN-TDM label, the node MUST verify
if the label is acceptable. If the label is not acceptable, the node
MUST generate a PathErr message with a "Routing problem/Unacceptable
label value" indication. Per [RFC3473], the generated PathErr
message MAY include an ACCEPTABLE_LABEL_SET object. With the
exception of label semantics, the upstream nodes processing a
received PathErr message and ACCEPTABLE_LABEL_SET object are not
modified by this document.
A received label SHALL be considered unacceptable when one of the
following cases occurs:
- The received label doesn't conform to local policy;
- An invalid value appears in the Length field;
- The selected link only supports 2.5 Gbps TS granularity while the
Length field in the label along with ODUk Signal Type indicates
the 1.25 Gbps TS granularity;
- The label includes an invalid TPN value that breaks the TPN
assignment rules; and
- The indicated resources (i.e., the number of "1"s in the Bit Map
field) are inconsistent with the Traffic Parameters.
Zhang, et al. Standards Track [Page 16]

RFC 7139 GMPLS Extensions for G.709 March 20146.3. Supporting Virtual Concatenation and Multiplication
Per [RFC6344], the Virtual Concatenation Groups (VCGs) can be created
using the One LSP approach or the Multiple LSPs approach.
In the case of the One LSP approach, the explicit ordered list of all
labels MUST reflect the order of VCG members, which is similar to
[RFC4328]. In the case of multiplexed virtually concatenated signals
(NVC > 1), the first label MUST indicate the components of the first
virtually concatenated signal; the second label MUST indicate the
components of the second virtually concatenated signal; and so on.
In the case of multiplication of multiplexed virtually concatenated
signals (MT > 1), the first label MUST indicate the components of the
first multiplexed virtually concatenated signal; the second label
MUST indicate components of the second multiplexed virtually
concatenated signal; and so on.
Support for Virtual Concatenation of ODU1, ODU2, and ODU3 Signal
Types, as defined by [RFC6344], is not modified by this document.
Virtual Concatenation of other Signal Types is not supported by
[G709-2012].
Multiplier (MT) usage is as defined in [RFC6344] and [RFC4328].
6.4. Examples
The following examples are given in order to illustrate the label
format described in Section 6.1 of this document.
(1) ODUk-to-OTUk Mapping:
In this scenario, the downstream node along an LSP returns a label
indicating that the ODUk (k=1, 2, 3, 4) is directly mapped into the
corresponding OTUk. The following example label indicates an ODU1
mapped into OTU1.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TPN = 0 | Reserved | Length = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(2) ODUj-to-ODUk Multiplexing:
Zhang, et al. Standards Track [Page 17]

RFC 7139 GMPLS Extensions for G.709 March 20147. Supporting Hitless Adjustment of ODUflex(GFP)
[G7044] describes the procedure of ODUflex(GFP) hitless resizing
using the Link Connection Resize (LCR) and Bandwidth Resize (BWR)
protocols in the OTN data plane.
For the control plane, signaling messages are REQUIRED to initiate
the adjustment procedure. Sections 2.5 and 4.6.4 of [RFC3209]
describe how the Shared Explicit (SE) style is used in the Traffic
Engineering (TE) network for bandwidth increasing and decreasing,
which is still applicable for triggering the ODUflex(GFP) adjustment
procedure in the data plane.
Note that the SE style MUST be used at the beginning when creating a
resizable ODUflex connection (Signal Type = 21). Otherwise an error
with Error Code "Conflicting reservation style" MUST be generated
when performing bandwidth adjustment.
- Bandwidth Increasing
For the ingress node, in order to increase the bandwidth of an
ODUflex(GFP) connection, a Path message with SE style (keeping
Tunnel ID unchanged and assigning a new LSP ID) MUST be sent along
the path.
The ingress node will trigger the BWR protocol when successful
completion of LCR protocols on every hop after the Resv message is
processed. On success of BWR, the ingress node SHOULD send a
PathTear message to delete the old control state (i.e., the
control state of the ODUflex(GFP) before resizing) on the control
plane.
A downstream node receiving a Path message with SE style compares
the old Traffic Parameters (stored locally) with the new one
carried in the Path message to determine the number of TSs to be
added. After choosing and reserving new available TS(s), the
downstream node MUST send back a Resv message carrying both the
old and new GENERALIZED_LABEL objects in the SE flow descriptor.
An upstream neighbor receiving a Resv message with an SE flow
descriptor MUST determine which TS(s) is/are added and trigger the
LCR protocol between itself and its downstream neighbor node.
- Bandwidth Decreasing
For the ingress node, a Path message with SE style SHOULD also be
sent for decreasing the ODUflex bandwidth.
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RFC 7139 GMPLS Extensions for G.709 March 2014
The ingress node will trigger the BWR protocol when successful
completion of LCR handshake on every hop after Resv message is
processed. On success of BWR, the second step of LCR, i.e., link
connection decrease procedure will be started on every hop of the
connection. After decreasing the bandwidth, the ingress node
SHOULD send a ResvErr message to tear down the old control state.
A downstream node receiving a Path message with SE style compares
the old Traffic Parameters with the new one carried in the Path
message to determine the number of TSs to be decreased. After
choosing TSs to be decreased, the downstream node MUST send back a
Resv message carrying both the old and new GENERALIZED_LABEL
objects in the SE flow descriptor.
An upstream neighbor receiving a Resv message with an SE flow
descriptor MUST determine which TS(s) is/are decreased and trigger
the first step of the LCR protocol (i.e., LCR handshake) between
itself and its downstream neighbor node.
8. Operations, Administration, and Maintenance (OAM) Considerations
OTN OAM configuration could be done through either Network Management
Systems (NMSs) or the GMPLS control plane as defined in [TDM-OAM].
[RFC4783] SHOULD be used for communication of alarm information in
GMPLS-based OTN.
Management Information Bases (MIBs) may need be extended to read new
information (e.g., OTN-TDM Generalized Label and OTN-TDM
SENDER_TSPEC / FLOWSPEC) from the OTN devices. This is outside the
scope of this document.
More information about the management aspects for GMPLS-based OTN,
refer to Section 5.7 of [RFC7062].
9. Control-Plane Backward-Compatibility Considerations
As described in [RFC7062], since [RFC4328] has been deployed in the
network for the nodes that support the 2001 revision of the G.709
specification, control-plane backward compatibility SHOULD be taken
into consideration. More specifically:
o Nodes supporting this document SHOULD support [RFC7138].
o Nodes supporting this document MAY support [RFC4328] signaling.
o A node supporting both sets of procedures (i.e., [RFC4328] and
this document) is not required to signal an LSP using both
procedures, i.e., to act as a signaling version translator.
Zhang, et al. Standards Track [Page 20]

RFC 7139 GMPLS Extensions for G.709 March 2014
o Ingress nodes that support both sets of procedures MAY select
which set of procedures to follow based on routing information or
local policy.
o Per [RFC3473], nodes that do not support this document will
generate a PathErr message, with a "Routing problem/Switching
Type" indication.
10. Security Considerations
This document is a modification to [RFC3473] and [RFC4328]; it only
differs in specific information communicated. As such, this document
introduces no new security considerations to the existing GMPLS
signaling protocols. Refer to [RFC3473] and [RFC4328] for further
details of the specific security measures. Additionally, [RFC5920]
provides an overview of security vulnerabilities and protection
mechanisms for the GMPLS control plane.
11. IANA Considerations
IANA has made the following assignments in the "Class Types or C-
Types - 9 FLOWSPEC" and "Class Types or C-Types - 12 SENDER_TSPEC"
section of the "Resource Reservation Protocol (RSVP) Parameters"
registry located at <http://www.iana.org/assignments/rsvp-parameters>.
Value Description Reference
7 OTN-TDM [RFC7139]
IANA maintains the "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Parameters" registry (see
<http://www.iana.org/assignments/gmpls-sig-parameters>). The
"Generalized PIDs (G-PID)" subregistry is included in this registry,
which is extended and updated by this document as detailed below.
Zhang, et al. Standards Track [Page 21]